Desired performance objectives for personal care absorbent products include low leakage from the product and a dry feel to the wearer. However, absorbent articles commonly fail before the total absorbent capacity of the product has been utilized. Absorbent garments, such as incontinence garments and disposable diapers, often leak at the legs and waist. The leakage can be due to a variety of shortcomings in the product, one being insufficient fluid uptake by the absorbent system, especially on the second or third liquid insults.
It had been found that urination can occur at rates as high as 15 to 20 milliliters per second and velocities as high as 280 centimeters per second. Conventional diaper absorbent structures, such as those comprising admixtures of absorbent gelling particles and cellulosic fluff pulp, may initially uptake fluids at rates of only 8 milliliters per second or less, based upon the web density and the concentration of the gelling particles. In addition, the initial uptake rates for conventional absorbent structures can deteriorate once they have already received liquid surges into their structures. The disparity between liquid delivery and uptake rates can result in excessive pooling on the surface of the fabric before the liquid is taken-up by the absorbent core. During this time, pooled liquid can leak from the leg openings of the diaper and soil the outer clothing and bedding of the wearer. Attempts to alleviate leakage have included providing physical barriers with such design features as elastic leg gathers and changing the amount and/or configuration of the absorbent material in the zone of the structure into which the liquid surges typically occur. Absorbent gelling particles have also been included to increase the liquid holding capacity in various regions of the absorbent structure, however, such absorbent gelling particles do not have the rapid uptake rates of conventional materials such as wood pulp and fluff which are also commonly used in absorbent cores. As a result, as the amount of absorbent gelling particles in the absorbent core structures are increased in modern day diapers, oftentimes the uptake rate will tend to decrease.
Nonwoven materials such as carded webs and spunbonded webs have been used as the body side liners in absorbent products. Specifically, very open, porous liner structures have been employed to allow liquid to rapidly pass through them and to help keep the body skin separated from the wetted absorbent pad underneath the liner. In addition, other layers of material, such as those constructed with thick, lofty fabric structures, have been interposed between the liner and absorbent pad for the purpose of reducing wet back.
With conventional fluff-based absorbent structures, the cellulosic fibers when wetted can lose resiliency and therefore collapse. As a result, the liquid uptake rate of the wetted structures may become too low to adequately accommodate subsequent liquid surges. Where absorbent gelling particles are incorporated between the fibers to hold them apart, the gelling particles swell and do not release the absorbed fluid. Swelling of the particles can then diminish the void volume of the absorbent structure and reduce the ability of the structure to rapidly uptake liquid.
The addition of more absorbent materials, such as secondary fluff pledgets, or absorbent gelling particles, have been employed to increase holding capacity. The desired rate of liquid intake within such arrangements, however, may not be sufficiently sustained during successive liquid surges.
Despite the development of absorbent structures of the types surveyed above, there remains a need for improved absorbent structures which can adequately reduce the incidents of leakage from absorbent products such as disposable diapers. There is therefore a need for a material and resultant product which can provide effective handling of liquid surges and which can more effectively uptake and retain repeated loadings of liquid during use.